Pattern controlled mechanism and tracer therefor



w. H. HOWE Dec. 31, 1935.

PATTERN CONTROLLED MECHANISM AND TRACER THEREFOR 11 Sheets-She s; 1

Filed Sept. 13-, 1932 Dec. 31", 1935. HQWE 2,025,748-

PATTERN CONTROLLED MECHANISM AND TRACER THEREFOR Filed Sept. 15,1932 I1 Sheets-Sheet 2 11M325; 'ZWZd/Z%W& y-

Dec. 31, 1935. w. H. HOWE 2,025,748

I PATTERN. CONTROLLED MECHANISM AND TRACER THEREFOR Fil ed. Sept. 13, 1932 11 Sheets-Sheet 5 5 {r if if; r

W. H. HOWE PATTERN CCNTRL'JLLED'MECHANISM AND TRACER THEREFOR Filed Sept. 13; 1932 ll Sheets-Sheet 4 Dec. 31, 1935. w ow -3 $025,748

'PATTIERN CONTROLLED MECHANISM AND TRACER THEREFOR Filed Sept. 13, 1932 '1-1' sh ds-sheet 5 Deaf 51,1935. w. H. HOWE "2,025,748

PATTERN CONTROLLED MECHANISM AND TRACER THEREFOR Filed Sept. 15, 1932 11 Sheets-Sheet 6- 7/ f if l A 1; I f i l 4 1H l L I I De.31, 1935. W.H. HOWE ,0

PATTERN CONTROLLED MECHANISM AND TRACER THEREFOR Filed Sept. is, 1932 11 Sheets-Sheet 7 Dei31,1935.' I w. H. HOWE 7 8" PATTERN CONTROLLED MECHANISM AND TRACER THEREFOR Filed Sept.- 15, 1952 -11 Sheets-Sheet 8 I JWQZZ? 3 ,1 M W Dec. 31, W. H. HOWE PATTERN CONTROLLED MECHAN I SM AND TRACER THEREFOR- Filed Sept. 15, 1932 11 Sheets-Sheet 9 1 w x Km m m ge SI 1 @l Z l I I v \I I I ly JMW -Dec. 31, 1935. w. H'. HowE. 2,025,748

PATTERN CONTROLLED MECHANISM AND TRACER THEREFOR Fil edsept. 15, 1932 11 Sheets-Sheet 10 g; fl

w 51 a/:2 7 wi /7% 7* w. H. HOWE I 2,025,748

* Dec. 31', 1935.

RATTERN CONTROLLED MECHANISM AND TRACER THEREFOR Fil ed Sept. 15, 1932 1 11 sheets-sheet 11 r, a r. 1, ,A W a ww y. w W @W i .Wl/WQ M m i. d, m. Wm P \f/r WW z m\ y. 1 UN w/l n W W by 3 W M 1 fl n 0 v /W f i W I) m 1W WT M 1 n? ww F v k i tern for its control, thus to facilitate variations of pattern. 1

mesa-sec. 1,1935;

' umrso 8mm 2,025,148 v PATTERN CONTROLLED MECHANISM AND TRACER..'IHlllilll-iltlt' won-ea E. Rowe,- Winchester, Mass., assignor'to' Atlantic Precision Instrument Compa Malden, Mass., a corporation of Massachusetts application September 13, 1932 Serial No. 632,937.

45 Claims.

problems arising in connection with such pat tern control consists in causing the tracer to accurately follow a pattern having abrupt shoulders in such a way that the tool will describe correspondingly abrupt shoulders relative to the work. Such a control ori'ollow-up system comprises in general the pattern, a tracer which .is moved along the pattern, a moving'system carrying the tracer, a tool, the work, and mechanism for moving the tool and work relatively responsive to small variations in the line of feed between the tracer and its supporting means and which at the same time tends to reduce these variations.

One of the objects of this invention is to provide a tracer mechanism so constructed that on engagement of the tracer with an abrupt shoulder on the pattern, it is given an immediate and rapid withdrawal to the extent necessary to clear the shoulder and to counteract frictional drag between it and the pattern in so doing.

Aiurther object is to provide a tracer which will immediately follow a sudden steep'depression in the pattern and cause the tool to make a correspondingly steep 'cut in the work. A further object is to provide a tracer mechanismwhich does not require a continuous pat- A still iurther object is to provide various types oi tool-controlling mechanism. responsive to the tracer mechanism.

' For a more complete understanding of this invention, reference may be had to the accompsnying drawings in which Figure 1 isa fragmentary top plan of a lathe provided with the pattern-controlled mechanism. Figure 2 is a section on line 2--2 of Figure 1. Figure 3 is a top plan, a portion of the tracer casing being broken away, of the pattern and the tracer mechanism.

Figure 4 is a section on line 4-4 of Figure 3.- Figure5isasectiononline HotFigurei. Figures 6, 7 and 8 are detail perspectives of certain portions-of the tracer mechanism.

Figures 9 to 12 inclusive are diagrammatic view illustrating the action of the tracer mechanism as the tracerencounters various pattern concontrolled tracer positions.

figurations and illustrating the. responses of the tool mechanism.

Figures 12a and 12b together'constitute a wiring diagram for control of a machine such as is illustrated in Figures 1 and 2.- f

Figure 13 is a diagrammatic view illustrating contours of tracer point and-tool for the tool topperate in accordance with the pattern, the idle side motions of the tracer being much ex-, aggerated.

corresponding 1 1o Figures 14 to 16 are diagrammatic views illustrating certain tracer positions corresponding to certain angular pressures exerted thereonas by contact with'a pattern.

Figure 17 is. a front elevation partly broken away showing a lathe having a pattern-controlled hydraulically-actuated tool.

' Figure 18 is a detail section on line i8l8. or I Figure 17..

Figure 194s a fragmentary top plan of the same;

Figures, 20 to.23 inclusiveare diagrammatic views illustrating the response of thehydraulic mechanisms to various pattern-controlled tracer positions.

Figure 24 is a fragmentary plan oi a tracer mechanism provided with electrical controlling-- devices. I

5 Figures 25 and 26 are detail sections on the correspondingly numbered section lines of. Figure 24. I v Figures 27 to 30 inclusive'are diagrammatic I views illustrating the response or the electricaltool-controlled mechanism using the tracer of Figures 24 to 26 inclusive, for various patterm.

. Figure 31 is a transverse section through a lathe having pattern controlled mechanical actuation oi. the cuttingitool. a a j Figure 32 is a detailed section on line 32-32 of Figure 31. I I

Figure 33-is a view similar to Figure 31 but to a larger scale. Figure 341s a detall;aection on line 8H4 oi figure-38.

Figure 85' is a top planet a discontinuous pata portion cl item and a tracer mechanism formed to coopierate therewith.

Figure as is a fragmentary side elevation of Figure 3'! is a detail section on of portion of Figure 85, but showing the tracer mechanism in a diflerent position relative to the Figure 38 is airagmentaryplan'similar to a" Figure 39 is'a detail. section on'line 33-43 ofFigure35.'

Figure 40 is a detail section online 40-40 of Figure 38.

By way of example this invention has been 11- lustrated as applied to a lathe, though it should be understood that it is applicable toa great certain of the control provided with a cylindrical post 33.-

variety of machines in which-the control of a tool with relation to work is to be produced through the action of a tracer with reference to a pattern and whether or not the tool is a cutting tool.

As shown in Figures 1 and 2 the lathe is provided with a conventional form of bed I on which is mounted for longitudinal sliding a traversing carriage 2. This carriage has mounted thereon for motion transver'seto its own motion a feed carriage 3. While various means might'be provided for moving these carriages, an electric motor F is shown for actuating the feed carriage to produce feed and retraction between the tool and the work and a similar motor (not shown in .these fi ures) may be used to effect the traverse mo-- tion as through a suitable lead. screw 4. On the feed carriage 3 is shown mounted a tool holder 5 carrying a tool 6. 4

The work W to be operated upon by the tool is carried by any suitable work support, herein shown as comprising centers carried by the lathe headstock l0 and the tailstock H, the headstock having a suitable driving connection to the work, as for example, the lathe dog l2. At l5 are shown supporting brackets for a table IS on which a, pattern may be fixed in any suitable manner. As shown the table I6 is provided with a series of electromagnet poles l8 which when energized retain the pattern securely thereon, the pattern being thus readily adjustable with respect to the table. or other magnetic material so that it may be held firmly by the magnet poles |8. Any other suitable means for holding the pattern might, however, be substituted andwthe pattern may be made of any suitablematerial.

The feed carriage 3 also-supports a tracer mechanism indicated generally at 20 having a tracer 2| mounted to be trayersed by the longitudinal motion of the carriage 2 along the edge contour 22 of the pattern. During this traverse the tracer'element 2| may be caused by means hereinafter described to move in and out to follow the pattern contour, small variations from a null relative position between the tracer element 2| and the remainder of'its mechanism acting to control the feed and retractive motions of the feed slide 3in corrective directions, the motion of this slide both in feed or retraction andin traverse being simultaneous with the movements of the tracer mechanism 20, so that the tool 6 may form on the work a contour similar to the pattern contour.

The tracer mechanism construction by which the tool motions may be controlled will now be explained. Referring to Figures 2 to 8, it will be noted that the mechanism 20', which is shown as enclosed within a casing 30, comprises a support 3| which is fixed relative to the base-320i the casing and so is mounted rigidly with the feed carriage 3.. For convenience in supporting parts, this support 3| is shown as This support carries for yielding motion in one direction in a plane a member 34, which as shown best in Figure 'I, may be a plateof rectangular outline with. a central opening 35 through which This pattern may be of steel shown, these springs being arranged in pairs on opposite sides of the member 34 engaging in 5 suitable notched recesses 31 in the support 3| and insimilar notched recesses 38 inthe member.34. Since these leaf springs 36 are of'substantial-width they prevent relative motion of the member 34 to the base 3|, except in a rec- 10 tilinear direction indicated by the arrow 2: in Figure 7.- This member 34 movably supportsa similar member 40, shown detached in Figure 6, to which is fixed the tracer 2| which extends out through an'opening in the casing 30 and im- 16 pinges on the pattern.- This member 40 is supported from the member 34 for motion in a line at an angle to the line of mbtion of the member a -34, as indicated by the arrow y in Figure 6. For

this purpose leaf springs 4| are shown as secured 20 in suitable recesses 42 in each of opposite sides of the member 40 and are also secured similarly as in recesses 43 in the member 34. Thus the tracer 2| is movable relative to the member 33 only in the rectilinear direction of the arrow 3;, 5 and the member 34 ismovable with respect to the base 3| only in the rectilinear direction of the arrow 2:. By compounding these motions, how-' ever, the tracer 2| is permitted a movement in all directions in a single plane with reference to the 30 base 3|. The tracer mechanism is so mounted on the feed carriage 3, however, that the line of feed and retraction is. between thepdirections indicated by the arrows a: and 1/, so that in order for the tracer 2| to move in the line of feed,' the member 40 must move relative to the member 34 in line with the arrow 1 and the member 34 must move with reference to the base 3| in' line with the arrow :0. While as shown both the members 34 and 40 are of rectangular outline 40 so that the directions of the arrows :1: and 11 are at right angles to each. other, this particular rein balanced condition when the tracer is in what may be termed a null position in which it exerts no efiect to actuate the feed slide in either direction. It is in this condition, as shown in Figure 3, when the pattern-engaging point 45 of the tracer is being moved along a contour such as c-d of the pattern which is parallel to the traverse direction of the carriage 2; Should the tracer point come to a depression in the pattern, as, for example, after leaving the pattern contour at. b as shown in Figure 9, the springs 36 and 4| immediately move the tracer inwardly from its null position and thereby act to operate the feed mechanism to feed the tool and the tracer as will later more fully appear. This forward motion of the tracer with reference to the support 3| is limited by two stops, these as shown being the screws 5|] and SI. The screw 56' is carried by an upstanding, arm 52 secured to thesupport 3| between the springs 36 on that side of the support nearest to the pattern and acts to limit the motion or the member 34 in the direction of the arrows inclined'toward the pat- 76 tern. The stop screw Bl is carried by a similar tern which might tend to actually prevent rearm 53 secured to the member 34 between the traction .of the tracer should the angle of force springs 4| which extend between the members. causing such retraction be limited to 90 from the 31 and 40, and thus acts to limit the movement line of'feed and retraction.

inclined toward the pattern.

of the tracer 40 by flexure oi the springs 4| with As hereinbefore pointed out, it is not essential reference to the member 34 in a direction-also that the directions of the movements between the This arrangement of the spring supports and ber relative to the member 34 be at right an stops insures that any force applied to the tracer gles to each other. Where th angl with re e the arm 2| in any of the directions shown by the eludes an electrical condenser plate 60 secured 3's tracer point in Figure 14), one being in the line traverse between the tracer and the pattern and so exerted throughout an angle oi more than 90. abrupt shoulder, the springs 36 and MY then 60 tracer to follow anundercut shoulder, a rectanthe mechanism in the control box 65 to energize which would apparently move the tracer point in cause of the sudden and marked increase of 7c tionaldrag between thetracer point andthepatwhile the deed continues slightly thereafter, 7 5

in the direction of the arrow 1 and inclined to motions ofthe tool and the tracer mechanism as the right. If, however, the pressure angle is 8. whole are shown diagr mmatically as of the removed with respect to longitudinal axis of the type more fully described a d claimed in the ap 'zs tracer arm 2|, as shown in Figure 15, the springs plication for patent of Albert Allen, Serial No. 4| cannot act, since the force is widthwise there- 9, filed May 4, 2301 Automatically nof, so that the motion of the tracer is backward trolled machine tool and follow-up system for arrows u, 1) and w in Figure 14,-member 40 is to a'suitable fixed portion of the tracer mechamoved relative to the member 84 in the direction nism which partakes of'the'motion of the tool car- I of the arrow 1 inclined toward the pattern until rier only, as, for example, the cylindrical post the member 40 against the stop screw 5|. At the angle br'acket'fil as shown in Figure 5. The tracer 40 same time the force on the tracer acts to move member dllwhich partakes of all the movements the member 36, flexing, the springs 36 in a direc of the tracer element 2% is shcwn as carrying a right and then diagonally rearwardly as shown between the member 40 and the post'33 and in 45 by the arrow 2 in Figure 14., The force in the di-- the null relative pcsition of the tracer-these plates rectionsoi any of these arrows u, v, and w may be define an electrical capacity of an amount which resolved into two forcesat right angles to each causes no motion of the feed motor F. The travother (see the small diagrams at the right of the arse motor T may then operate to efiect relative of the arrow :1: and in the direction ,to retract the between the tool and the work without any feed 4 point more than 90 removed from the retractthe tracer is traversing any portion of the pating direction of the tracer as shown by theartern parallel to the line of traverse.

row 'wacts to'retract rather thanto advance the v Supposing now, as in; Figure 9 the tracer tracen Of course should the direction oftraverse point reaches the shoulder b so that it becomes be in the reverse direction tothat shown, a force unsupported by the edge o1 the pattern at an on the other side of the lineoi feed and retraction immediately throw the tracer forwardly into the gular shoulder: being all that it is called-upon to the feed motor to feed the tool into the work and encounter and follow, nevertheless the angle bethe tracer toward the patternand at the same teed rather than retraction direction, but which capacity between the plates and 83. Thus actually causesthe retraction of the tracer, as the tool feeds in straight and-produces an abrupt I previouslydescribeiproducesacomponent or reshoulder on the work. This takes place untiltracting force which tends to'overcome any fric-' the'tracer, being stopped by the pattern at cv quency vacuum backward, as previously explained, suddenly separating the condenser plates from their null relation, which acts to stop the traverse motor and to actuate the-feed motor in the reverse direction' to withdraw as the traverse motor has withdrawn the tool and the tracer sufficiently for the condenser plates to return to their null relation, the feed motor is stopped and the traverse motoragain takes up its load as previously. Such a condition is illustrated in Figure 11 where the tracer has just passed the shoulder f. I

Where the tracer is moving up or downan inclined path both the work feed motor and the traverse motor are actuated. The tracer going down the incline is shown in Figure '12, in which the condenser plates 60 and 63 are closer than at their null position, but never sufficiently far from their null relation to actually stop the traverse motor T.

In Figures 12a and 12b is shown a diagram of one arrangement by which the traverse and feed control may be actuated by the variable capacity due to variable spacing of the condenser plates 60 and 63 of Figures 9 to 12 in accordance with the Allen application hereinbefore mentioned. The leads 450, 452, 45s are common to these two Figures 12a and' 12b. Capacity variations due to variable spacing of the condenser'p'lates 00 and 03, change the tuning of a including the condenser plates and a whole at 50! in Figure 12a and thus vary the voltage induced in this secondary circuit. As shown this voltage is amplified by the radio iretube amplifier unit at 502 and it is then re tified and filtered hy rectifying and filtering units 503 and 506 to produce a substantrally direct current flow through the resistors 505 and 505 and consequently to produce a substantially smooth direct current potential across each of these resistors which varies in amount in accordance with changes in capacity due to space changes between the condenser plates 60 and 63.

These direct current voltages together with prop- V er amounts of direct current voltage from a drop resistor 501 of a power supply unit 508 and alternating current voltage oithe proper phase and magnitude from the unit 509 are used to control the grid circuits of power gas filled tubes 5 and'5l2 which control the direction and rate of motion of the feed motor F. Such a power tube passes cathode-plate current whenever the grid is biased sufliciently positive and when once opened continues to pass such current as long as this current remains inthe same direction regardless of subsequent grid bias. -By'the combination of the alternating and. direct voltage bias herein employed the time in each positive half cycle at which cathode-plate current starts to pass is controlled, this current passing for the remainder of this half cycle so that the power passed to the variable speed feed motor and consequently the speed or thismotor is dependent on this voltage bias. The. connections from the resistor-$105 and 506 are reversed to the power tubes 5 and in (see Figure 120) so that-the both the tool and the tracer from the pattern and work respectively, As soon voltages being so secondary circuit 53 and an inductance 500, relative to resonance withan exciting oscillatory vacuum tube circuit indicated as tool both in. the line of The circuit constants are so adjusted that in null 5 condition of the condenser plate neither tube to actuate the motor F, but if the .capacity is less thannull the tube 5 l2 passes cur rent and the feed motor F operates in a direction to increase this capacity, moving the tracertoward the pattern until it is stopped and the capacity is brought back to null, and if the capacity is more than null the tube 5| l passes current and the eed motor F operates in the reverse direction. T ese tubes feed to the reverse di-' 15 rection'motor field windings 5|3 and 5H, re- 'spectiveiy,- of the feed motor.

The control of each of these tubes 5 and 512 is also modified by the direct current voltage across the armature as a corrective follow up to prevent excessive over-travel of this motor in either direction.

The control of the traverse motor T is efiected by the power tube 5l5, the grid of which is biased by suitably phased alternating current voltagegs from the unit 509, direct current voltage from the resistor 501, and direct current voltage derived. from the voltage across the armature of the feed motor F smoothedout by a suitable choke and condenser. This latter voltage is 30 made the controlling variable, the other biasing arranged and adjusted that with the feed motor running at full speed in either direction the traverse motor is stopped and with the feed motor stopped the traverse motor is running at full speed, and with uniform complementary speed variations of these motors in between stopped and full speed. This complementary speed variation provides for all slopes of taper of the tool operating on the work from 4 zero to 90" Power for the feed and traverse motors, which are direct current variable speed motors, is derivedfrom the transformer 5l5.

That portion of the diagram of Figure 12b to the right of the dotted lines 520 relates to manual and automatic control for returning the traversing carriage to its starting position after the completion of a traverse and while the tracer and thetool are held retracted from the pattern and work, respectively,-and-is 5 v herein.

v.Other means for accomplishing this control, not dependent on capacity changes of a condenser, will be later explained in which the same relationship of co-ordinate control of the feed and traverse motors is employed. ,Thecondenser mechanism, however, afiords a' control mechanism continuously variable with variations of the tracer from null position andTmakes possible continuous motor control of great accuracy so that accurate pattern control is possible.

i From the foregoing description it will be noted that the tracer point is movablerelative to the traverse and. that the lateral motion-in the line of traverse is ineffective, that in the line-of teed being the one which is relied upon to produce the corrective control of the tool to followthe pattern. 'In Figure 13 is shown diagrammatically ,thernanner in which this relative of'the feed motor to act 20.

to 524 inclusive 45 lateral motion 76 may be'-.-correc'tedfor a the accuracy 01' motion or the tool in following the contour of the work i and how it corrects for variation from null 01' the greater than i thisrelative side motion.

-- with .the 'correspcndingpositionsof the tool in tracer. This is done by forming the work-enand'the pattern-em gaging portion of the tool gaging portion of the tracer of the same contours except that the tracer pointis madeof a width that of the tool by the amount 01 Thus in Figure 13 the tracer point contours are shown in dotted'lines solid lines, following a curve which takesin all angular pressures to which the tracer is subjected by its engagement with the pattern contour.

Thus, assuming a travel in the direction of the arrow shown in this figure, as the tracer passes downwardly into a contour valley asatlmit is fortion of traverse as at wardly of the position point is in exact alinement therewith in the directern. As the tracer engages a portion of the pattern of less depth the tracer is then moved back of its null position, which actuates the feed mechanism in the reverse direction to withdraw the tool,

whereupon the tool is projected slightly inwardly of its corresponding tracer position and the tracer engages the pattern slightly forwardly of thecorrespo-nding of the tool by, the amount of side slip and is slightly inwardly of it by rea- 1|. The tracer is then drawn slightly backwardly with relation to the tool by its frictional engagement with the pat-- pressure and exhaust sides.

. pipe H5. Thus graduating the sizes proper ratios of traverse and retraction may be motions havebeen much exaggerated in order to better show the principle 'of operation.

In Figures 17 to 23 inclusive a fluid pressure, preferably hydraulic, actuation of the traverse and feed and retractive motions controlled by the 5 in so far as its motion in the line of feed is concerned. I

The sizeoi the valve cylinder l03from both The-pressure pipe 40 I01, however, communicates the traversing cylinder. I00 so that the tracer mechanism,

and to the pattern. i

In Figure 21 the tracer is shown as beingtravhand end or the feed cylinder luothrough the there is both traverse and withdrawal of the tool so that a taper cut results} By of the 'port' openings the .unitormtaper." 1- It now the tracer impinges on a shoulder on the pattern, the alve HII is driven i'urther outwardly'fnom the null positionga's shown in Figure- 23, in which position the suppl or flf ld pressure to thetraverse cylinder; I00 is cut oil. by the por- 11193; of the valve so that the oi the is being traversed relatively to the work 45 only being in operation. When the and 203 riding in Q the tool and the tree "m tracer tent further than that shown in Figure 28, breaking the connection between. the contacts 200 and the feed motors contacts at,20 0 'still in eng gement ration as shown in Figure 22, it immediately feeds forward rapidly causing the valve H0 to assume supply of cylinder I00 is cut off by and pressure is supplied through the pipe M1 to the outer end of the feed cylinder I03 while the inner end of this cylinder is open to the discharge through the pipe H0 beyond the end of the valve H0 adjacent to its portion H3. The feed carriage is then fed inwardly to form a sharp shoulder similar to that on the pattern, the. feed cylinder base of this depression is reached by the tracer, a slight forward movement of the feed beyond this brings the tracer back to its null relation, whereupon the conditions shown in Figure 20 are resumed with the traverse cylinder in operation and the feed cylinder inoperative.

In Figures 24 to 29 a simplified electrical control mechanism is illustrated. Carried by a portion of thetracer mechanism, as, for example, the post 33, are four spring contacts 200, 20!, 202

tracer, as by being mounted on the tracer member 50, are a pair of contact posts 20 and 205 which may impinge the spring contact p'ns 2M and 202 and similar abutment contacts 201 and 208 may impinge on the contact pins 200 and 203, respectively. The pin 20l is longer than the pin 202 and pin 200 is longer than the pin 203, so that on backward motion of the tracer in the direction of retraction tact is first made between the 20! and then on contacts 200 and further motion contact is also made between the contacts 205 and 202, while on motion of the tracer in the feed direction connection is first made between the contacts 201 and 200 and then between the contacts 208 and 203. These contacts are connected to control F and traverse motors T, preferably through suitable relays in the cbntrol box 2l0. In the null position of the tracer the contacts at 201 and 200and 200 and 20! are closed together, respectively, thus completing the circuit through the traverse motor to produce relative traverse between the tool and the work and between the'tracer and the pattern, respectively, thus producing a straight out on the work conforming to a portion of the pattern parallel to the line of traverse. If now the tracer is moved outwardly, as by engaging with an outwardly tapered face of the pattern, as shown in Figure 28, the tracer is moved backwardly from its null position, thus bringing the contact 205 into engagement with the contact 202, energizing the feed. motor F in a direction to withdraw r mechanism from the work and the pattern, respe tively, but so long as the tracer is not too far from its null position, the and 201 and 2M and.204 are so that the traverse motor being operated- This results in a taper If nowthe tracer impinges the work as in Figure 29, the is suddenly moved backwardly to an exis still be enthe valve portion H3 the contact 208 .tacts 20| and 204 so that tubes 206. Rigid with thev taper at a constant angle of the tool carriage, con- 3|3 within 1 carriage 2b. When-this shoe the lead screw 300 but by stopping the members the tracer from the pattern. Since there is no longer any traverse motion, the'tool is brought directly outwardly by this retractivemotion of the ieed motor, thus forming an abrupt shoulder on the work corresponding to that on the pat- 5 tern. If now the tracer falls off an abrupt shoulder on the pattern, the tracer moves forwardly so far from its null position that both the contacts 204 and 205 are withdrawn from connection with their mating contacts 20! and 202, while is' brought into operative engagement with the contact 203. This energizes the feed motor to feedthe tool and the tracer into the work and pattern, respectively, while the traverse motor is disconnected. In case an inward 5 taper is engaged by the tracer the tracer does not move inwardly sufficiently to separate the conthe traverse motor as well as the feed motor is energized. Thus the tool is given a motion both of traverse and in- 20 ward feed so that a tapered cut results. It will be noted that. there is no provision here for a graduated speed relation between the traverse and feed motors so that the taper would always be cut at a definite angle. However, if this an- 25 gle should not be that of the pattern, there would result a slight over or under feed, depending on whether the pattern taper were more or less than that provided by the normal relative speed and this would result in periodic stopping or starting 30 of one or the other of these motors, thus cutting the fixed motor ratio and straight in or straight traverse motions, the general direction of all being that of the taper of the pattern.

In Figures 31 to 34 a mechanical control of the traverse and feed is illustrated. Referring to these figures, the traverse of the carriage 2b is produced by rotation of a lead screw 300 while the feed I and retraction of the carriage 3b is produced by rotation in opposite directions of the feed screw 30!. This feed screw is arranged to be driven in either of opposite directions through friction clutches-shown at 302 and 303. Each of these clutches has a member as 300 and 305, respectively, freely journaled on the feed shaft with either of which the feed screw may be coupled and these members 300 and 305 are each provided with a bevel gear as 306 and 301 which mesh with a common drive gear 300 so that they are driven continuously in. opposite directions. This gear 308 is shown as driven through interand 310 from a continuously driven The lead screw 300 is also continuously driven and has thereon a cylindrical nut 3l2 provided with a peripheral groove which may engage a friction shoe 3% 315 to a portion MB of the traversing 3 is out of engagement with the nut 3l2 it rotates freely with its rotation thereagainst, it is lead screw and is pivoted at as by pressing the shoe 3 held from rotation with the forced to traverse Also continuously driving members 320,- 32l and shown are geared together so that 321 and 322 rotate in opposite directions and the-member 32;! rotates in'the di rection of the member 322. Within each of these members "320, 32l. and 322, as shown best in Figures 33 and 34, are pivoted at 323 arcuate 322 which as brake shoes such as 324 which may have frictional material on'their outer faces, and these 75 lengthwise thereof ,moving the v traversecarriage 2b therewith. rotated are three shoesmay be pressed apart as by rocking a cam element 320 positioned between their free ends soas to engage their respective rotary members to which is connected an arm 321 connected in turn by a link 320 tothe shoe 3l4 so'that when for example, to the plate 40:

- the brake members of the drive member 320 are expanded, the member 320 is rocked in a direction to move the brake shoe 3i4 from the ut 3i2 thus to operatively disconnect the lead screw from the traverse carriage 212 so as to stop its traverse. The brake elements within the drive members 32i and 322 are carried by disks 330 and 33L "respectively, which are both connected through arms 332-and 333 with a rod 334 connected to the lever 330 which on rocking in either of opposite directions connects one or the other of the friction clutches 302 and 303 with the feed screw. These parts are so adjustedthat a small moveinent of theflever applies a differential force to the clutches 302 and 303, either one of which may preponderate to produce a resultant motion of the feed screw, while in mid-position of the lever 335 both friction clutches are equally effective and the feed screw remains stationary. The cams .325 of the drive members 320, 32! and 322 are connected together as by the links 340, 3 and 342 with a lever 343 fulcrumed at 344 on the carriage 3b, the upper end of which is pivotally secured at 345 to the tracer carrier, as,

When the tracer is in its null position the parts are as shown inFigure 31. Neither of the driving elements 32! or 322 preponderates to move the rod 334, which is thus held in its central position, holding the frictional clutches 302 and 303 equally effective so that no motion of the feed screw results. There is thus no feed motion of .-the tool 6 relative to the; work W. At the same time the shoe 3 is in firm engagement with the nut 3l2 so that the traversing screw is effective to produce-traverse of the tool relative to the work and. the tracer relative to the pattern. -If now the tracer is moved outwardly as by reaching an outwardly inclined portion of the pattern, the lever 343 is rocked, tightening the brake elements against the drive member 322 and loosening the brake elements in-the' drive dition, pulling the bar 334 inwardly and produca greater frictional drag at the clutch 302 than at the clutch 303, thus starting the rotation of the feed shaft in a direction to retract the tool from the work and the tracer from the patterm- The speed of motion of the feed shaft is.

dependent on the amount of variation of the tracer-from its null position as this determines the frictional overalan ce ofthe driving element.322'from the of the element 32l andtheextent of movemen the rod 334. At the same :time' the friction elements within the driveimembar 323 are brought intodrivingsengagement with this member'so as to more or less withdraw 'f frictional engagement'tending to hold the nut 3l2 rotation, which thus produces a less eifective traverse connectionso that the. speed .oi traverse is slowed. The extent of this slowing also dependent-on the amount of motion of the tracer away from its null position, which is determinedby the amount of the taper of the pat- "It tern. -Thus the speeds of retraction and traverse of the tool are adjusted in accordance withthe taper of the pattern to operate on the work in accordance with the taper of thepattern.

If an abrupt shoulder is contacted by the tracer, the amount of its motion away from its. null position is relatively large, as has been on the pattern. Should the tracer, on the other hand, meet with a receding taper on the work, the lever 343 would be swung in the reverse direction, rendering the driving member 32! more effective than the member 322, thus moving the rod 334 in the opposite direction and causing the frictional engagement of the clutch 303 to be greater than that ot'the clutch 802, thus to rotate the feed screw in a direction to feed the tool into the work and the tracer toward the pattern while the driving member 320 would also be rendered effective to somewhat reduce the brakon the work conforming to the. sharp shoulder I crease the speed of traverse. Should the tracer fall on a sharpshoulder on the pattern, it would move immediately further from its null position in feeding direction which would further increase the driving eifect of the; clutch 303 over that of the clutch 802, increasing the speed of inward feed of the tool and tracer and stoppingv the traverse by completely freeing the nut M2 to rotate with the lead screw 300. The actuating mechanism for the. rod 334 and the shoe 3 l4 thus constitutes an amplified power follow-up mechanism control.

In some cases it may befdesirable for ease in building up any desired pattern -to" provide a mechanism by which the pattern need not be continuous over those portions where a straight traversing feed of the tool is desired. This permits the use ofseparate blocks for building up the pattern as shown for example in Figure 35, wherein the blocks 400, 40!, 402, 403 and 404 are supported on a suitable table 400 on which they may be held as by forming this'table as a magnetic table which may be energized from any convenient source of electric current. to hold the block thereto with great tenacity. It will'be noted that these blocks-define a-con-' figuration along their front edges which is discontinuous between the blocks 403 and 402 and elsewhere continuous. the forward faces of the blocks 402 and403 being in alinementand parallel with the direction ,of traverse. The block 404 is associated with the. block 403' to; provide areceding shoulder overthe edge 400. The block 402 has a similarbut shorter receding shoulder at its edge 401. The normal presents a straight forwardface 409' parallel 'wl the traverse direction.- The tracer 2| is e're so related to its controlling mechanism-whatever .this maybe, that it is normally 'held'in null relation as heretofore described, so that when its endis free the tracer will be in null position and the traversing mechanism oniywillbe eflective. It will thus remain in any poiition relative tofeed a tapered 'face at 400 andthe block 400"presents'.

and retraction in which it may'flnd itself at any time and thus define a straight out along the work parallel to the direction-of traverse. It

' will thus jump gaps in the discontinuous contour line of ;the pattern as between the blocks 402 and 403, which it could not do if,it were biased by its supporting springs to other than the null position.

Means. are provided with this mechanism, therefore, to produce atemporary bias away from null position wherever the pattern configuration is such that feed is required. This -means,. as shown, comprisesan element 4l5 which follows along behind the tracer in its traversing movement and with which cooperate certain parts of the pattern. This element M5 as shown best in Figures 36 and 37 is formed as a vane, depending from pivotal supporting portions 416 at opposite ends from a supporting frame 4!? carried by the tracer casing 30. As shown this frame All is substantially triangular in outline. Normally'the vane M5 hangs perpendicular or nearly so, and preferably in contact with an adjustable stop screw 418 carried in a bracket arm 419 forming part of the frame 422 acts in opposition to the supporting springs 38 and 46 of the tracer as heretofore described,

in so far as their tendency to hold the tracer forwardly from its null position is concerned, but by relieving the tension on the spring 422 the mounting'springs 3' and 4| are effective to bias the tracer toward the pattern, or in feed direction, away from its null relation. The spring 420, however, is sufilciently strong to hold the tracer in null position so long as the vane M5 remains'vertical. Certain of the pattern blocks,

however, or certain parts of these blocks, are

made higher than others in position to engage the vane during the traverse and rock its lower end backwardly relative to the traverse direction, it being noted from Figure 36 that the-vane M5 is positioned above the level of the tracer 2|.

Referring now to Figure 39, it will be seen that the block 402 is sufliciently high to engage the lower edge of the vane 4| 5 and as the tracer passes along theforward face of this block and is about to pass over the shoulder portion 401, the vane has impinged on the block 402 and has been rocked to the position shown in Figure 40, so that the tracer is then biased by its supporting springs to press against the pattern so that when it.

passes over, the shoulder 401 it immediately moves 409 of the bleck .400, it is heldfrom inward feed.

and consequently it is no longer necessary to bias the tracer for inward motion from its null position, hence the block 400may be a low block over whichthevane'l I Smay pass without impingement thereon so that it may drop to its normal position. Likewise the block 404 should be a high block to cause the tracer to feed inwardly over its shoulder 406, while the block 403 is a low block so that by the time the tracer reaches the discontinuous portion of its travel between the blocks 403 and' following into the valleys and jumping discontinuous portions at constant elevations or depths.

While as shown the tool and tracer mechanism are mounted for movement, it will, of course, be evident that it might in some cases be found desirable to move the work rather than the tool in traverse or feed, or both, and that the pattern instead of the tracer mechanism might be movable either in traverse or feed, or both.

It should be understood that the foregoing description of certain embodiments of this invention has been given merely by way of example and that many other modifications and changes might be made without departing from the spirit or scope of this invention as defined by the appended claims.

I claim:

1. In combination, a tracer unit comprising a support, a tracer, resilient means for supporting said tracer from said support, and stops for limiting the lateral motion of said tracer relative to a rectilinear path in one direction, said resilient means being disposed to cause pressure exerted against said tracer throughout an angular range ofat least 90 from said path to produce movement of said tracer having a component in one direction along said path, and a device responsive to position variations between said tracer and said supportalong said path.

2. In combination, a tracer unit comprising a support, a tracer, resilient means for supporting ber carried by said'support for movement relative thereto in a rectilinear direction, a tracer carried by said member for movement relative thereto in a rectilinear direction angularly disposed to said first-mentioned rectilinear direction, said unit including means tending to hold said member and tracer in definite relative positions, and a device responsive to position variations between said tracer and support. I

4. Atracer unit comprising a support, a member carried by said support for-movement relative thereto in a rectilinear direction, a tracer carried by said member for movement relative thereto in a rectilinear direction angularly disposed to said first-mentioned linear direction, said unit including means for yieldingly holding, said member and tracer out of their respective normal positions,

and a device responsive to position variations-between said tracer and said support.

5.-A follow-up system including a comprising a support, a member carried ,by said support for yielding movement in, a rectilinear direction, a tracer carried by said member for yieldsive to position changes of said tracer relative to 6. In combination, a support, a member carried by'said support for yielding movement in a rec'-' 'tilinear direction, a tracer carriedby said member for rectilinear movement relative thereto in a direction angularly disposed to said flrst-mentioned movement, and a control device responsive only to movement of said tracer relative to said support in a rectilinear direction between said relatively angularly disposed directions.

'7. A tracer unit comprising a support, a member carried by said support for movement relative thereto in a rectilinear direction, a tracer carried by said member for movement relative thereto in a rectilinear direction ansulariy dis-.

posed to said first-mentioned rectilinear dlrection, means for limiting the motions of said member and of said tracer relative to said member each in one direction from a normal position, said unit including means for yieldingly holding said member and tracer out of their respective normal positions, and a device responsive to position variations between said tracer and said support.

8. In combination, a unit comprising a support, a member carried by said support for move- -ment relative thereto in a rectilinear direction,

a tracer carried by said member for movement relative thereto in a rectilinear direction angularly disposed to said first-mentioned rectilinear di rection, said unit including yielding means tending to hold said tracer in one position relative to said support, and means for moving saidsupport controlled by the relative positions of said tracer and support and inactive only when said tracer is ina position relative to said support different from said one position.

. 9. In combination, a tracer unit comprising a support, a member carried by said support for movement relative thereto in a linear direction, a tracer carried by said member for movement relative thereto in a linear direction angularly disposed to said first-mentioned linear direction, said unit including means for yieldingly holding said -member and tracer out of their respective 10. In combination, a tracer unit comprising asupport, a member carried by said support for movement relative thereto in a. linear direction, a tracer carried by said member for movement relative thereto in a linear direction angularly disposed to said flrst-mentioned linear direction, means for limiting the motions of said member and of said tracer relative to said member each in one direction from a normal position, said unit including means for yieldingly holding said member and tracer out of their respective normal positions, a controlling device responsive to position variations between said tracer and support, and means controlled by said device inoperative only when said tracer and said support are in their respective normal positions.

11. A tracer unit comprising a support, a member carried by said support for movement relative thereto in a linear direction, a'tracer carried.- by said member for movement relatiVeTtheret'o in a linear direction angularly disposed to said firstmentio'ned linear direction, said unit including means for yieldingly holding said member' and 6 tracer in their respective normal positions, adevice responsive to; position .variations between said tracer and said support, and means acting under predetermined conditionsto bias said yielding means'to move said trader and member out of their respective normal positions.

12. A tracer unit comprising a support, a member carried by said support for-movement relative thereto in a linear direction, a tracer carried by said member for movement relative thereto in a linear direction angularly disposed to said fi'rstmentioned linear direction, means for limiting the motions of said member and of said tracer rela-' tive to said member each in one direction from a normal position, said unit including means for 20 yieldingly holding said member and tracer in their respective normal positions, a device responsive to position variations between said tracer and said support, and means acting under predetermined conditions to bias .said yielding25 means to move said tracer andmember'out of their respective normal positions.

13. In combination, a tracer mechanism comprising a support, a member spring-supported from said support for movementrelative thereto 30 14. In combination, a tracer mechanism com 40 prising a support, a member spring supported from said support for movement relative thereto in a plane substantially parallel to said support and limited to one angular direction, a member spring-supported from said first-mentioned member for movement in a plane substantially parallel thereto and in' a diflerent angular direction from the motion of said first-mentioned member,

means for limiting the extent of movement of each of said members, and means responsive to the relative positions of said support and said sec ond-mentioned member.

15. In combination, a tracer mechanism comprising a support, a set oileaf-springsupstanding from saidsupport in parallel relation, .a platecarried by said springs spaced from said support and movable by flexing of said springs in one linear direction only, a set of leaf springs. up-- standing from said plate with their flexing directions angularly disposed to the line of motion of 0 said plate relative to said support, a member carried by said second set of leafsprings, means for moving said member-relative to said support, and means responsive to such movement from a predeterminedrelative position.

r 16. In combination, a .tracer mechanism comprising a support, a post extending from said .support, a pair of plates each having a hole through which said post loosely passes, means for.supporting said plates from said support, the 7 next adjacent plate with capability of motion I transversely of said post. in one linear direction only and the other plate from said adjacent plate with capability of motion relative to said adjacent p ate in one direction only angularly relatedto 7'5 

